CN106772281A - Multichannel SAR system channel calibration method based on sliding window filtering - Google Patents
Multichannel SAR system channel calibration method based on sliding window filtering Download PDFInfo
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- CN106772281A CN106772281A CN201610959393.8A CN201610959393A CN106772281A CN 106772281 A CN106772281 A CN 106772281A CN 201610959393 A CN201610959393 A CN 201610959393A CN 106772281 A CN106772281 A CN 106772281A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
- G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
- G01S13/9021—SAR image post-processing techniques
- G01S13/9029—SAR image post-processing techniques specially adapted for moving target detection within a single SAR image or within multiple SAR images taken at the same time
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/40—Means for monitoring or calibrating
- G01S7/4004—Means for monitoring or calibrating of parts of a radar system
- G01S7/4021—Means for monitoring or calibrating of parts of a radar system of receivers
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
- G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
- G01S13/9004—SAR image acquisition techniques
- G01S13/9005—SAR image acquisition techniques with optical processing of the SAR signals
Abstract
The invention discloses a kind of Multichannel SAR system channel calibration method based on sliding window filtering, comprise the following steps：S1, determine reference channel with passage to be calibrated；S2, by data conversion to two-dimensional frequency domain；S3, the sample data selected in sliding window；S4, calculating filter coefficient；S5, sliding window filtering；S5, transform the data into back two-dimensional time-domain.The present invention realizes simply, without iterative operation, sliding window filtering process being carried out by two-dimensional frequency domain, effectively increases the correlation of interchannel, can finally improve the clutter recognition ratio of clutter recognition processing links.The present invention is applied to the compensation that a variety of Multichannel SAR systems are carried out with inter-channel level and phase error, such as airborne, spaceborne and missile-borne Multichannel SAR.
Description
Technical field
The present invention relates to physical field, and in particular to a kind of Multichannel SAR system based on sliding window filtering is led to
Road calibration method.
Background technology
In synthetic aperture radar (SAR) field, the moving target in SAR image be generally submerged in strong clutter background and
Cannot be distinguished.To distinguish moving target, doppler filtering technology need to be used, be examined outside the Doppler frequency band of clutter
Survey.But pulse recurrence frequency is generally selected smaller by SAR system in order to obtain relatively wide mapping strip width, so that in advance
Leave detection zone outside the clutter band for carrying out moving object detection for also little.Along with clutter and moving target in SAR echoes
Doppler frequency spectrum all by serious broadening, therefore the frequency spectrum of moving target and clutter generally has overlapping, causes merely in clutter
The performance that band carries out outward moving object detection is very limited.Limit and can be moved in clutter band inner region in order to avoid this
Target detection, the most frequently used and maximally effective solution is：The spatial domain free degree obtained using multichannel technology completes clutter
Suppress, moving object detection is then carried out again.In order to obtain preferable clutter recognition performance, it usually needs to the amplitude of interchannel
Compensated with phase error, namely needed into row of channels calibration process.
At present, in synthetic aperture radar passage collimation technique is mainly carried out in two-dimensional frequency domain.Ender is in document
“J.H.G.Ender,‘The airborne experimental multi-channel SAR system AER-II,’in
Proc.EUSAR,Self-adaption two-dimensional calibration (A2DC) is proposed in Germany, Mar.1996, pp.49-52. "
Method, passage calibration is completed in two-dimensional frequency domain in the way of adaptive iteration.Additionally, Gierull is in document
“C.H.Gierull,‘Digital channel balancing of along-track interferometricSAR
Data, ' DRDC, Ottawa, ON, Canada, Tech.Rep.TM 2003-024, Mar.2003. " in introduce and a kind of be referred to as solving
The method for tiltedly processing (de-trending), the method is realized simply, but it only compensates for the interferometric phase inclined-plane of interchannel,
And do not compensated then for range error.Therefore, also critically important occasion is compensated for some range errors, is more likely to
Selection A2DC methods.Another interesting method is document " M.Soumekh, ' Signal subspace fusion of
uncalibrated sensors with application in SAR and diagnostic medicine,’IEEE
What is proposed in Trans.on Image Process., vol.8, no.1, pp.127-137, Jan.1999. " is empty based on signal subspace
Between treatment (SSP) passage collimation technique, the method projected to by reference image data institute by by view data to be calibrated
In the signal subspace of sign, the compensation of the amplitude and phase error of interchannel is completed.Due to the signal subspace in SSP methods
Represent with signal projection etc. operation it is very time-consuming, be more likely in practical application selection A2DC methods, but A2DC methods shortcoming
It is to need to be iterated operation.
The content of the invention
In order to solve the above technical problems, the invention provides a kind of Multichannel SAR system based on sliding window filtering
System channel calibration method, amplitude and phase error compensation that slide window processing realizes interchannel, nothing are carried out by two-dimensional frequency domain
Iterative operation is needed, is realized simple.
The purpose of the present invention is achieved through the following technical solutions：Multichannel SAR system based on sliding window filtering
System channel calibration method, comprises the following steps：
S1, determine reference channel with passage to be calibrated：
Some passage is selected from multiple parallel channels as reference channel, and other passages are passage to be calibrated；
S2, the data of reference channel and passage to be calibrated are converted into two-dimensional frequency domain using two-dimensional Fourier transform；
S3, the sample data selected in sliding window；
S4, using in sliding window sample calculate filter coefficient；
S5, sliding window filtering：Filter coefficient is utilized in two-dimensional frequency domainTreat calibrated channel and enter row of channels school
It is accurate；
S6, using two-dimentional inverse Fourier transform, the channel data conversion after calibration is back to two-dimensional time-domain.
Wherein, the passage to be calibrated in the step S1 is adjusted according to reference channel.
Wherein, the computing formula of the step S4 median filter coefficients is：
In formula, Zref(kr,ka) and Z2(kr,ka) the two-dimensional frequency numeric field data of reference channel and passage to be calibrated is respectively,
(·)*Expression takes the conjugate operation of plural number, krAnd kaThe sample point sequence number in frequency of distance domain and Doppler frequency domain is represented respectively,
ΩallIt is the coordinate set of two-dimensional frequency domain entirety data, ΩwinTo fall into the coordinate set of data in sliding window, and Ωwin∈Ωall。
Wherein, the sliding window filtering operation in the step S5 is described as：
In formula, Z2,cal(kr,ka) be passage to be calibrated by the data after calibration,It is filter coefficient, Z2
(kr,ka) be passage to be calibrated two-dimensional frequency numeric field data.
Compared with prior art, the invention has the advantages that：
1st, compared to A2DC methods, the present invention is realized simple without iterative processing steps；
2nd, compared to SSP methods, the present invention carries out adaptive weight training in two-dimensional frequency domain, does not have numerous and diverse and time-consuming
Signal subspace represent with the operation such as signal projection, have the advantages that method flow design is simple, speed is fast and performance is good；
3rd, (de-trending) method is processed compared to oblique solution, the present invention compensate for range error and phase error simultaneously, have
There is more excellent performance.
Brief description of the drawings
Fig. 1 is the Multichannel SAR system channel calibration side based on sliding window filtering provided in an embodiment of the present invention
The operational flowchart of method.
Fig. 2 is the passage 2 before and after calibration and the amplitude imbalance between reference channel 1.
Fig. 3 is the average amplitude ratio after being normalized with the passage 2 before and after 1 pair of calibration of reference channel.
Fig. 4 be passage 2 it is calibrated after residual phase difference.
Specific embodiment
With reference to specific embodiment, the present invention is described in detail.Following examples will be helpful to the technology of this area
Personnel further understand the present invention, but the invention is not limited in any way.It should be pointed out that to the ordinary skill of this area
For personnel, without departing from the inventive concept of the premise, various modifications and improvements can be made.These belong to the present invention
Protection domain.
As shown in figure 1, the embodiment of the invention provides a kind of Multichannel SAR system based on sliding window filtering
Channel calibration method, specifically includes following steps：
The data of synthetic aperture radar of multichannel is input into first.For the consideration of optimal letter miscellaneous noise ratio coherent processing, it is assumed that
The data to each passage have carried out the treatment such as Range compress and range migration correction.Without loss of generality, only consider to two
The situation that passage is calibrated.
Step 1, determine reference channel with passage to be calibrated.Some passage is selected from multiple parallel channels as reference
Passage namely main channel, without loss of generality, generally selected passage 1.And other passages are passage to be calibrated namely from passage.This
When, passage to be calibrated is adjusted according to reference channel.The inventive method is set as a example by being calibrated to passage 2 below
Meter.
Step 2, by data conversion to two-dimensional frequency domain.The data of passage 1 and passage 2 are become using two-dimensional Fourier transform
Two-dimensional frequency domain is shifted to, Z is designated as respectivelyref(kr,ka) and Z2(kr,ka), krAnd kaRepresent frequency of distance domain and Doppler frequently respectively
The sample point sequence number in rate domain.
Step 3, the sample data selected in sliding window.Before calibration, the sample fallen into sliding window need to be picked out
Data, for the calculating of filter coefficient, sliding window size usually used in practice is 3 × 3,5 × 5 or 5 × 3.
Step 4, calculating filter coefficient.Using the sample estimation filter coefficient in sliding window.The meter of filter coefficient
Calculating formula is：
In formula, ΩallIt is the coordinate set of two-dimensional frequency domain entirety data, ΩwinTo fall into the coordinate set of data in sliding window,
And Ωwin∈Ωall, ()*Expression takes the conjugate operation of plural number.
Step 5, sliding window filtering.Filter coefficient is utilized in two-dimensional frequency domainEnter row of channels calibration to passage 2,
The operation is described as：
In formula, Z2,cal(kr,ka) it is passage 2 by the data after calibration, now itself and the amplitude between reference channel data
Error and phase error have been obtained for compensation.
Step 6, by data become be back to two-dimensional time-domain.Using two-dimentional inverse Fourier transform, the channel data after calibration is become
Gain to two-dimensional time-domain.Now, the range error and phase error between passage to be calibrated and reference channel data have been obtained
Compensation.
Effectiveness of the invention can be verified by following experiment.Experiment X-band measured data used is derived from
Certain airborne Multichannel SAR experiment.In order to realize the function of Ground moving target detection, the antenna of experimental system
It is arranged using along course.Radar parameter is as follows：Carrier frequency 9GHz, pulse recurrence frequency 840Hz, doppler bandwidth
530Hz, doppler centroid -90Hz, platform speed 110m/s, antenna sub-aperture interval 0.4m.The actual measurement used in experiment
Initial data is about 8m × 8m through the image resolution ratio after SAR imagings.
Fig. 2-Fig. 4 has carried out performance comparison to the inventive method and A2DC methods (iterations is 3), examines using this
The amplitude and phase imbalance situation of the interchannel before inventive method and A2DC methods are calibrated to passage 2 and after calibration.In Fig. 2
Four performance curves are shown, they are followed successively by passage 1, passage 2, the passage 2 calibrated through the inventive method and through A2DC side
The average amplitude spectrum obtained at the passage 2 that method was calibrated.Fig. 3 is shown the ratio of average amplitude, and it is by putting down passage 1
Equal amplitude spectrum is obtained than the average amplitude spectrum (before calibration or after calibration) of upper channel 2.For clarity, be only show in Fig. 3
Result in main lobe wave beam.As can be seen that the performance of the inventive method is closer to ideal performance curve, namely closer to
Average amplitude is than the situation for 1.Same conclusion can also be obtained from Fig. 4.From fig. 4, it can be seen that the last phase of the inventive method
Position is unbalance to be closer to ideal situation, namely 0rad situation.Thus, it can be concluded that the inventive method can obtain preferably logical
Road calibration performance.
Table 1 gives the performance comparison result of the inventive method and A2DC methods, makees which employs clutter recognition ratio (CSR)
It is performance indications.In experiment, the iterations of A2DC methods is 3.The definition of CSR indexs is：Power before clutter recognition with
Power ratio value after suppression.As it can be seen from table 1 the inventive method performance compared with A2DC methods is more excellent.
The performance comparison result of table 1
Specific embodiment of the invention is described above.It is to be appreciated that the invention is not limited in above-mentioned
Particular implementation, those skilled in the art can within the scope of the claims make various deformations or amendments, this not shadow
Sound substance of the invention.
Claims (4)
1. the Multichannel SAR system channel calibration method for being filtered based on sliding window, it is characterised in that including following step
Suddenly：
S1, determine reference channel with passage to be calibrated：
Some passage is selected from multiple parallel channels as reference channel, and other passages are passage to be calibrated；
S2, the data of reference channel and passage to be calibrated are converted into two-dimensional frequency domain using two-dimensional Fourier transform；
S3, the sample data selected in sliding window；
S4, using in sliding window sample calculate filter coefficient；
S5, sliding window filtering：Filter coefficient is utilized in two-dimensional frequency domainTreat calibrated channel and enter row of channels calibration；
S6, using two-dimentional inverse Fourier transform, the channel data conversion after calibration is back to two-dimensional time-domain.
2. as claimed in claim 1 to be based on the Multichannel SAR system channel calibration method that sliding window is filtered, it is special
Levy and be, the passage to be calibrated in the step S1 is adjusted according to reference channel.
3. as claimed in claim 1 to be based on the Multichannel SAR system channel calibration method that sliding window is filtered, it is special
Levy and be, the computing formula of the step S4 median filter coefficients is：
In formula, Zref(kr,ka) and Z2(kr,ka) it is respectively the two-dimensional frequency numeric field data of reference channel and passage to be calibrated, ()*
Expression takes the conjugate operation of plural number, krAnd kaThe sample point sequence number in frequency of distance domain and Doppler frequency domain, Ω are represented respectivelyallFor
The coordinate set of two-dimensional frequency domain entirety data, ΩwinTo fall into the coordinate set of data in sliding window, and Ωwin∈Ωall。
4. as claimed in claim 1 to be based on the Multichannel SAR system channel calibration method that sliding window is filtered, it is special
Levy and be, the sliding window filtering operation in the step S5 is described as：
In formula, Z2,cal(kr,ka) be passage to be calibrated by the data after calibration,It is filter coefficient, Z2(kr,ka)
It is the two-dimensional frequency numeric field data of passage to be calibrated.
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Cited By (3)
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| CN108872983A (en) * | 2017-05-11 | 2018-11-23 | 北京遥感设备研究所 | A kind of Missile-borne SAR imaging self-focusing method |
| CN109814175A (en) * | 2019-02-14 | 2019-05-28 | 浙江省气象台 | A kind of satellite-based strong convection monitoring method and its application |
| CN113419240A (en) * | 2021-04-26 | 2021-09-21 | 中国科学院空天信息创新研究院 | Moving target detection method based on dual-channel SAR, dual-channel SAR and storage medium |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108872983A (en) * | 2017-05-11 | 2018-11-23 | 北京遥感设备研究所 | A kind of Missile-borne SAR imaging self-focusing method |
| CN109814175A (en) * | 2019-02-14 | 2019-05-28 | 浙江省气象台 | A kind of satellite-based strong convection monitoring method and its application |
| CN113419240A (en) * | 2021-04-26 | 2021-09-21 | 中国科学院空天信息创新研究院 | Moving target detection method based on dual-channel SAR, dual-channel SAR and storage medium |
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